In general, infrared radiation (IR) sensors are used in a variety of applications to detect infrared radiation and provide an electrical output that is a measure of the incident infrared radiation. IR sensors typically use either photonic detectors or thermal detectors for detecting the infrared radiation. Photon detectors detect incident photons by using the energy of the photons to excite charge carriers in a material. The excitation of the material is then detected electronically. Thermal detectors also detect photons. Thermal detectors, however, use the energy of said photons to increase the temperature of a component. By measuring the change in temperature, the intensity of the photons producing the change in temperature can be determined.
Photonic detectors typically have higher sensitivity and faster response times than thermal detectors. However, photon detectors must be cryogenically cooled in order to minimize thermal interference, thus increasing the cost, complexity, weight, and power consumption of the device. In contrast, thermal detectors operate at room temperature, thus avoiding the cooling required by photon detector devices. As a result, thermal detector devices can typically have smaller sizes, lower costs, and lower power consumption than photon detector devices.
One type of infrared thermal detector is a bolometer. A bolometer includes an absorber element for absorbing infrared radiation and a transducer element that has an electrical resistance that varies with temperature. In operation, infrared radiation incident upon the bolometer will be absorbed by the absorber element of the bolometer and the heat generated by the absorbed radiation will be transferred to the transducer element. As the transducer element heats in response to the absorbed radiation, the electrical resistance of the transducer element will change in a predetermined manner. By detecting changes in the electrical resistance, a measure of the incident infrared radiation can be obtained.
Because bolometers must first absorb incident electromagnetic radiation to induce a change in temperature, the efficiency of the absorber in a bolometer relates to the sensitivity and accuracy of the bolometer. Ideally, absorption as close to 100% of incident electromagnetic radiation is desired. Recent advances in technology have enabled the absorber element of a bolometer to be formed by atomic layer deposition (ALD). ALD enables absorber elements to be formed as thin metal films with precise and uniform thickness. ALD thin film bolometers are typically capable of greater absorption efficiency than non ALD thin film bolometers. While traditional ALD thin film bolometers devices and methods of fabrication are effective, there is always a need to improve the efficiency, simplify the fabrication, and/or decrease the production costs of such devices.